1. Field of the Invention
The present invention relates to a facility of collecting a component having higher melting point as compared with other constituent components in a gas. More particularly, the present invention relates to a facility suitable for collecting a di-halogenated aromatic compound in a gas discharged accompanying dehydration treatment, in production of a polyarylene sulfide resin (hereinafter, referred to simply as PAS).
2. Description of Prior Art
Conventionally, polyarylene sulfide resins such as a polyphenylene sulfide resin (hereinafter, referred to simply as PPS) are known as an engineering resin excellent in mechanical strength, heat resistance and the like and having high rigidity.
For producing this PAS, there are methods disclosed, for example, in Japanese Patent Application Publication (JP-B) No. 52-12240 (production method of p-phenylene sulfide polymer), and Japanese Patent Application Laid-Open (JP-A) Nos. 2-180928 (production method of polyarylene sulfide), 6-248077 (production method of polyarylene sulfide having high molecular weight), 7-207027 (production method of polyarylene sulfide), 7-228698 (production method of polyarylene sulfide) and the like.
These methods have an approximate process in which a di-halogenated aromatic compound such as polydichlorobenzene (PDCB) and the like and an alkali metal sulfide such as sodium sulfide, lithium sulfide and the like are subjected to a polymerization reaction in an aprotic organic solvent such as N-methyl-2-pyrrolidone (hereinafter, simply referred to as NMP). In producing PAS by these methods, when the water content of a reaction substance is controlled before the polymerization reaction or during the polymerization reaction, PAS having higher molecular weight can be produced, therefore, in general, dehydration treatment is conducted by a distillation tower and the like.
However, when production of PAS is conducted continuously by these methods, a component of higher melting point as compared with other constituent components such as a di-halogenated aromatic compound and the like mixes in a gas discharged from a distillation tower into which a reaction substance is fed continuously, and is discharged together. Therefore, when such a gas is cooled, there is a possibility that a di-halogenated aromatic compound and the like contained therein solidify and adhere to a discharge tube and the like to clog the tube.
Therefore, now, a di-halogenated aromatic compound C in a gas G is tried to be collected by a recovering apparatus 100 shown in FIG. 1, and the like.
Namely, in the collecting apparatus 100, by first opening only 101A of gate valves 101A and 101B, the gas G into which the di-halogenated aromatic compound C mixes is fed in a first condenser 103A through a feeding tube 102A. In this time, an atmosphere in the first condenser 103A is cooled to temperatures lower than the melting point of the di-halogenated aromatic compound C by a refrigerant IW such as cooling water and the like. Therefore, in the first condenser 103A, the di-halogenated aromatic compound C in the gas G solidifies, and the gas G discharged through a discharge tube 104A does not receive mixing with the di-halogenated aromatic compound C. After conducting the above-mentioned treatment for given time, then, the gate valve 101A is closed and the gate valve 101B is opened, and the gas G into which the di-halogenated aromatic compound C mixes is fed into a second condenser 103B through a feeding tube 102B (switching of this treatment does not need the lapse of time, and sometimes needs change of the temperature of the gas G discharged from the condenser 103A, change of the temperature of the refrigerant IW passed through the condenser 103A, change of the pressure of the gas G fed to the condenser 103A, and the like). In this time, an atmosphere in this second condenser 103B is cooled to temperatures lower than the melting point of the di-halogenated aromatic compound C by a refrigerant IW. Therefore, in the second condenser 103B, the di-halogenated aromatic compound C in the gas G solidifies, and the gas G discharged through a discharge tube 104B does not receive mixing with the di-halogenated aromatic compound C. On the other hand, during feeding of the gas G into this second condenser 103B, an atmosphere in the first condenser 103A is heated to temperatures higher than the melting point of the di-halogenated aromatic compound C by a heat medium HW such as hot water and the like. Therefore, the di-halogenated aromatic compound C solidified in the first condenser 103A is melted, and discharged from the bottom through a discharge tube 105A, and collected. After given time of the above-mentioned treatment, flow through of the gas G is switched to a feeding tube 102A, and the same operation as described above is repeated. Thus, the di-halogenated aromatic compound C in the gas G is collected.
Problems to be Solved by the Invention
However, in the case of the above-mentioned collecting facility, switching of the flow through route of the gas G is required, therefore, the operation is not continuous, leading to poor treating efficiency. During no passing through the gas G, the temperature of the gas G remaining in the feeding tube 102A or 102B lowers, and sometimes, the di-halogenated aromatic compound C solidifies and adheres, therefore, the feeding tubes 102A, 102B have to be hot-insulated. This not only causes loss of energy but also makes a complicated structure of the facility.